PO:24:070 | Preliminary descriptive data from a single-centre cohort of patients with idiopathic inflammatory myopathy: focus on paraneoplastic and non-paraneoplastic patients

Silvia Ebe Lucia Della Pina¹, Paola Bizioli¹, Samantha Mazza², Caproli Alessia¹, Cesare Tomasi¹, Ilaria Cavazzana¹, Franco Franceschini¹. | ¹S.C.O. Reumatologia ed Immunologia Clinica, ASST Spedali Civili di Brescia, Università degli Studi di Brescia, Brescia, Italy; ²Università degli Studi di Brescia, Brescia, Italy.

Background. Idiopathic inflammatory myopathies (IIMs) are a group of autoimmune disorders with heterogeneous clinical manifestations. The discovery of myositis specific autoantibodies (MSAs) brought great advances, because they are strongly associated with distinct clinical phenotypes and different prognosis. Among MSAs, anti-TIF1(a-TIF1) antibodies are considered a strong serologic marker for cancer-associated myositis (CAM, defined as myositis arising ± 3 years from cancer diagnosis). Approximately 70% of DM patients a-TIF1+ are diagnosed as having concominant cancer. The aim of this study is to describe our cohort of IIMs patients, focusing on CAM patients and IIM cases with a history of cancer.

Materials and Methods. Medical records of 213 IIM patients followed up at our Myositis Clinic were reviewed. The demographic data, diagnosis, autoantibodies, laboratory profile, instrumental and clinical features at onset were collected.Patients with a history of cancer were then considered and divided into 2 groups: the first one, named “Concomitant” (CC), composed by CAM cases, and group 2, named “Not concomitant” (NCC), consisting of IIM patients with neoplasia onset outside the 3-year period.Normality of the distributions was assessed using the Kolmogorov-Smirnov test. Continuous variables were presented as means ±SD and compared with Student’s T-test. Categorical variables were presented as frequencies or percentages and compared with Chi-Square test and the Fisher’s exact test, as appropriate; associations of the crosstabs were verified using standardized adjusted residuals. A two-sided alpha level of 0.05 was used for all tests.

Results. Data from the entire cohort were showed in Table 1. Within the cohort 28,6% (N=61) of patients developed a malignancy: 30 patients defined as CC group (49.2%) and 31 patients as NCC one (50.8%). DM was the IIM most frequent in CC group (p=0,025) and ASS in NCC one (p=0,043). As shown in Table 3, no clinical features are significantly associated with CC, while ILD (p=0,018), dyspnoea (p=0,034), arthritis (p=0,018), sclerodactyly (p=0,036) and mechanic's hands (p=0,048) are significantly associated with the absence of a paraneoplastic IMM.A-TIF1 antibody was found associated (p=0,005) with the CC group, while a-Jo1 antibody was mostly detected in the NCC group (p=0,002). MAA rates did not differ within the two groups. The most represented cancer in CC group was breast cancer (50%), followed by ENT and prostatic (16,7% and 16,6% respecitively). Metastatic cancer was found in 53,6%. A significantly higher number of stage IV cancer was found in the CC group compared to the NCC group (p=0,023) where instead a significant prevalence of stage 1 and 3 was recorded (p=0,006 and p=0,011 respecitively). No differences in the number of deaths were observed between the two groups.

Conclusions. Anti-TIF1 is the only serological marker of CAM. These patients showed a more aggressive cancer since the IIM diagnosis with frequent metastasis rate, compared with IIM with a non concominant cancer.